Tectonically induced, deep-burial paleo-collapses in the Zhujiang Miocene carbonate platform in the northern South China Sea

• DOI: 10.1016/j.margeo.2015.03.007
• Publication Date: 2015-04-05T20:03:45Z
• Authors: Duanxin Chen; Shiguo Wu; David Völker; Dongdong Dong; Hesheng Shi; Shujuan Zhao; Lichun Zhu
• Keywords: Sinkhole; Carbonate platform; Mud volcano; Breccia

3D seismic reflection data image more than 400 circular depressions in the top surface of the buried Zhujiang carbonate platform of the South China Sea. The features range between 100 and 900 m in diameter and appear to be points of origin of vertical pipes in the overlying 900 m thick mudstone unit The depressions in the carbonates are explained as karst solution features (sinkholes). Unlike similar features in drowned carbonate platforms elsewhere, carbonate solution in the South China Sea apparently took place after drowning and burial of the platform and not under meteoric exposure. The spatial clustering of the sinkholes along faults that are related to the tectonic Dongsha Event suggests that faults acted as pathways for corrosive fluids that served as agents of carbonate solution. Karst cave collapse formed depressions both in the top surface of the carbonate and in the overlying strata. Seismostratigraphic relations between faults, a regional unconformity, the fill of the pipes and the surrounding strata help to reconstruct the succession of events leading to these spectacular features. The corrosive fluids were most probably derived from pore waters of the sandstones underlying the carbonate platform, bearing acidic components thought to be produced from the bacterial degradation of oil. (C) 2015 Elsevier B.V. All rights reserved.